Advanced CMOS (complementary metal-oxide-semiconductor) and BiCMOS (bipolar and complementary metal-oxide-semiconductor), as well as some other device technologies, require the formation of doped N or P wells or both N and P wells in bulk silicon or epitaxial (for example, a P.sup.- epi-layer on a P.sup.+ substrate or an N.sup.- epi-layer on an N.sup.+ substrate) wafers. The well formation process is usually based on ion implantation of boron (for P-well) or phosphorus (for N-well) followed by a long (e.g., a few hours), high-temperature (e.g., 1100.degree. to 1200.degree. C.) furnace anneal in an inert (argon or nitrogen) or oxidizing (oxygen or steam) ambient.
The relatively long furnace anneal process is required to form relatively deep N and P well regions via thermal diffusion. The well junction depth is usually at least a few times larger than the source/drain junction depths. For instance, a 0.35.mu.m CMOS technology may require N and P wells with greater than one micron well-to-substrate junction depth.
If the well formation process is to be performed using a single-wafer processing, the time and temperature requirements for a single-wafer well drive-in process can be rather excessive (e.g., temperatures of 1100.degree.-1200.degree. C. for more than 30 min.) resulting in low manufacturing throughput. This requirement could increase the manufacturing costs.
Moreover, conventional furnace diffusion processes for formation of diffused wells cause lateral diffusion of both N and P dopants, resulting in lateral dopant compensation. This undesirable lateral diffusion places a limit of the minimum N-to-P well spacing and makes device layout scaling more difficult.
As a result, there is a need for an RTP (rapid thermal processing) based well formation process which can form the necessary N and P well regions using reasonable RTP temperature/time conditions. Moreover, there is a need for a well formation process which can form the wells of desired depths using reduced temperature/time process parameters without excessive lateral interdiffusion of the N and P well dopants.